Finite strain continuum damage model

This is a finite strain damage model for hyperelastic materials. The damage reduction factor is only applied for the isochoric portion of hyperelastic constitutive models. The multiplicative split of the deformation gradient is utilized to decouple the strain energy function into volumetric and isochoric portions. It is assumed that the damage only affects the isochoric part of the deformation. The results reveal the effectiveness of damage softening approach and its application for any desired hyperelastic formulation.